154 
Proceedings of the Royal Society. 
seems little doubt, however, that in these cases the compounds are 
much more difficult to obtain. 
In the second place, the true character of these bodies is still 
uncertain. It is certain that the substances described by Messrs 
Haas and Cffive, as well as those obtained by us, were not pure 
substances but mixtures. Haas states that he endeavoured to 
obtain the peroxides of zinc free from admixed hydrate, but that he 
never succeeded in producing the precipitation of peroxide when 
the formation of hydrate was prevented with sufficient care (sorg- 
faltig genug). This statement is, however, too indefinite, and leaves 
one very much in the dark. It is easy to prepare ammoniacal 
solutions of zinc salts which remain perfectly clear when diluted 
with three or more times their bulk of water, but in which the 
addition of their own volume of hydrogen peroxide solution pro- 
duces an abundant precipitate. This behaviour makes it difficult 
to understand how the formation of the zinc peroxide is necessarily 
a secondary product depending upon a previous formation of 
hydrated oxide. Our experiments lead us to a quite contrary con- 
clusion, viz., that the hydrated oxide is a secondary product, the 
result of the decomposition of the peroxide. The mere determin- 
ation of the peroxide oxygen and of basic oxide does not give a 
satisfactory insight into the composition of these bodies unless the 
absence of acids (carbonic, nitric, &c.) is proved. How far this 
was the case with the substances obtained by Herr Haas cannot be 
gathered from his paper. Our preparations, as well as those of M. 
Cleve, contained one or other of these acids. We expect shortly to 
be in a position to communicate the results of the continuation of 
our researches to the Society. 
6. On Supersaturation. By W. J. Nicol, Esq. 
PRIVATE BUSINESS. 
The following Candidates were balloted for and declared duly 
elected Bellows of the Society: — Professor Steggall ; James Pringle, 
Esq. ; A. P. Laurie, Esq., B.Sc. ; B. J. Harvey Gibson, Esq. ; Pro- 
fessor Dyce Davidson ; and George Smith, Esq. 
